1. Technical Field
The present invention relates to an impact sensitive damper damping vibration transferred from a road surface to a vehicle, and more particularly, to an impact sensitive damper in which handling stability may be achieved in a low speed operating section of the damper and improvement of ride comfort may be achieved in a high speed operating section thereof.
2. Description of the Related Art
Generally, since vibration or impact is continuously applied from a road surface through wheels during driving of a vehicle, a damping device is installed between a car body and a car axis to prevent the impact or the vibration from being directly transferred to the car body, thereby improving ride comfort and to suppress irregular vibration of the car body, thereby improving handling stability.
Here, a connection device between the car body and the car axis, including this damping device is collectively referred to as a suspension device. The suspension device is configured to include a chassis spring alleviating impact, a damper controlling free vibration of the chassis spring to thereby improve ride comfort, a stabilizer preventing rolling, a rubber bushing, a control arm, and the like.
Among other components of the suspension device, the damper serves to suppress and damp vibration from a road surface and is mounted between the car body or a frame and a wheel. Particularly, the damper absorbs vertical vibrational energy of the car body to suppress the vibration, improve the ride comfort, protect loaded freight, and decrease dynamic stress of each part of the car body, thereby increasing durability. In addition, the damper suppresses downward movement of a spring to secure ground properties of a tire and suppresses a change in posture due to inertial force to improve movement performance of a vehicle.
The ride comfort and the handling stability may be appropriately adjusted according to damping force characteristics of the damper. That is, the damping force needs to be small in order to improve the ride comfort during general driving of the vehicle and the damping force needs to be large in order to improve the handling stability at the time of quick turning of the vehicle or during high speed driving thereof.
FIG. 1 is a cross-sectional view showing a general damper according to the related art.
The damper 40 includes a cylinder 43 having operating fluid filled therein, a piston rod 49 having one end positioned inside the cylinder and the other end positioned outside of the cylinder, and a piston valve 47 mounted on one end of the piston rod 49 to thereby reciprocate within the cylinder 43. The cylinder 43 is configured of an inner pipe 41 and an outer pipe 42 and has a body valve 48 mounted in a position facing the piston valve 47 at a distal end thereof.
An inner portion of the cylinder is divided into a compression chamber 52 and an expansion chamber 51 by the piston valve 47, and the inner pipe 41 and the outer pipe 42 have a storing room 46 formed therebetween.
FIG. 2 is a cross-sectional view of a body valve for describing generation of damping force of a damper.
As shown in FIG. 2, the body valve 48 includes compression channels 61a and expansion channels 61b vertically formed in a body valve body 61 and a suction valve assembly 66 mounted on an upper portion of the body valve body 61, wherein the compression channels 61a and the expansion channels 61b allow the compression chamber 52 and the storing room 46 to be in communication with each other and the suction valve opens/closes the compression channels 61a. 
The suction valve assembly 66 includes slots 62a and a single-plate suction valve 62 that are formed at the upper portion of the body valve body 61 and a retainer 63, a suction spring 64, and a washer 65 that are sequentially stacked on the slots and the suction valve, wherein the slots are in communication with the compression channels 61a, the suction value 62 opens/closes the expansion channels 61b, and the washer 65 supports the retainer 63 and the suction spring 64.
Here, the retainer 63 maintains a clearance, the suction spring 64 elastically supports a rear surface of the suction valve 62 at an upper portion of the retainer 63 and always closely adheres the suction valve 62 to an upper surface of the body valve body 61, and the washer 65 having holes 65a formed therein is mounted on an upper portion of the suction spring 64. The body valve body 61 includes a multi-plate disk 68 mounted on a lower portion thereof, wherein the multi-plate disk 68 opens/closes the compression channels 61a. 
At the time of the compression stroke of the piston rod 49, operating fluid of the compression chamber 52 passes through the holes 65a of the washer 65, the slots 62a of the suction valve 62 and the compression channels 61a and then pushes the multi-plate disk 68 downwardly to move toward the storing room 46 while opening the multi-plate disk 68, thereby generating the damping force. At the time of the expansion stroke thereof, the operating fluid in the storing room 46 passes through the extension channels 61b and then pushes the suction valve 62 upwardly to move to the compression chamber 52 while opening the suction valve 62, thereby generating the damping force.
However, in the case of the body valve 48 according to the related art using the above-mentioned multi-plate disk 68, as a load applied to the multi-plate disk 68 increases, a deformation amount rapidly decreases. Therefore, when large impact is transferred to the damper, a limitation in deformation of the multi-plate disk 68 occurs, such that the damping force rapidly increases, thereby deteriorating the ride comfort.